DK10FG-6050A2491301-MB-A03 missing ACOK

[bridges_4u]

Hi there,

I have a DK10FG-6050A2491301-MB-A03 motherboard with missing ACOK voltage. Here are the basic voltages of BQ24725A. The motherboard is dead with no signs of life.

ACN : 19.35V
ACP : 19.36V
ACDET : 2.7V
REGN : 5.916V
VCC : 19.36V

Diode mode to ground reading on ACOK rail is 0.450V on pin 1 of R6013 and 0.230V at pin 2. Replaced BQ24725A a couple of times. Still no luck.

The problem was that I was not having 3.3V/5V from the TPS51225 regulator. So I tracked down to the BQ24725A which was missing the ACOK voltage needed to turn on the EC. As per my knowledge, ACOK should be 3V. Am i missing something ?

Any help would be appreciated. More details can be shared as we move along for diagnostics.

Regards

[bridges_4u]

Just wanted to add that ACDRV is ~25v.

Regards

[Sephir0th]

You are likely on the wrong path here.

First counterargument: ACOK is not even used (left floating) on some devices, so basically inconclusive then.

Second counterargument: if ACOK is pulled up by a 3.3V rail instead of REGN, then it is inconclusive too, since without a working 3.3V, ACOK can't be HIGH.

Sounds logical, doesn't it?

If i have to bet, i'd say your embedded controller is either shorted or simply not powered with (the same) 3.3V.

EDIT: Did not look into the schematics, but regarding what mon2 shared, it seems you have indeed to move to the 3.3V LDO and the corresponding Enable (EN0).

[mon2]

1) it is late for you.

2) yes, U6100 must be enabled to create the pull-up voltage needed by the resistor @ R6013 which is camped onto the open-drain circuit @ ACOK. If the ACOK line is floating when the charger IC believes the adapter voltage is OK, someone needs to pull-up this floating line to park it. This voltage is from U6100 (P3V3AL).

PAD6100 shows that this same voltage is linked to VRP3V3A.

3) With no power to the board / no battery - what is the RESISTANCE to ground of L6100? This rail must be enabled through EN_3V_5V.

What is the voltage to ground of EN_3V_5V?

U6100 IC datasheet:

Dual-Synchronous, Step-Down Controller with Out-of-Audio™ Operation and 100-mA datasheet (Rev. E)

ACOK = ACPRES and used by U301 (EC)

[bridges_4u]

@ Sephir0th,

Thank you for sharing your knowledge. I would like to point out something that i found about the ACOK in the datasheet for U6000.
"ACOK : AC adapter detection open drain output. It is pulled HIGH to external pull-up supply rail by external pull-up resistor when voltage on ACDET pin is between 2.4V and 3.15V, and voltage on VCC is above UVLO and voltage on VCC pin is 275mV above voltage on SRN pin, indicating a valid adapter is present to start charge. If any one of the above conditions can not meet, it is pulled LOW to GND by internal MOSFET. Connect a 10kΩ pull up resistor from ACOK to the pull-up supply rail.."

This led me to believe that the ACOK voltage is being generated by U6000 and send to enable the SIO.

mon2 ,

It has been a long time. Thank you for stepping in to help.
Resistance at L6100 to ground : 5.63kOhms
voltage to ground of EN_3V_5V : 0V.

Thank you guys again for your inputs and knowledge. Where do we go from here?

[mcplslg123]

Have you flashed EC bios?

[Sephir0th]

Since P5VAUXON is asserted from U7490, you want to check whether P3V3_LDO is present. You can alternatively measure at U6100 Pin8. Voltage and resistance to GND.

[bridges_4u]

@mcplslg123,

I have not flashed the EC as I have not changed it yet.

Sephir0th

Yes. I have 3.3V at pin 4 of U7490.

U6100
Pin 8: 3.3V
Resistance to GND (Pin 8) : 2.018 M Ohms

Regards

[bridges_4u]

Sephir0th mon2


Just an update.

Felt that U6100 was not properly seated. Fluxed and locked the IC in place.

Now i get the following voltages at U6100.

Pin 18 : 3.3v
Pin 8 : 3.3v
Pin 16 : 19.36V
Pin 3 : 2V

VREG5, ENTRIP1 &2 are still missing. Any pointers?

No voltages on VCC, AVCC & VDD on U301.

[mon2]

What is the voltage to ground of pin 17 on U6100? (VRP5V0A_LDO = VREG5)

[bridges_4u]

mon2 Sephir0th

VREG5 on U6100 : 0.00V

[mon2]

With no power, measure the resistance to ground of VREG5.

[bridges_4u]

With no power, measure the resistance to ground of VREG5.

mon2 Sephir0th

VREG5 (Resistance to GND) : 59.1K Ohms

[mcplslg123]

Either the IC is bad or badly soldered or EC bios is corrupt.

[bridges_4u]

mcplslg123 mon2 Sephir0th

I just changed the TPS51123 with a brand new one. Now I get

ENTRIP 1 : 1.4V
ENTRIP 2 : 1.2V
VREG3 : 3.3V
VREG5 : 5V
EN_3V_5V : 3.3V
VIN : 19.36V

But I do not get any voltage at L6100 & L6150. I tried changing Q6100, Q6101, Q6150 & Q6151. Reseated L6100 & L6150. There is no shorting at neither pins of the coils after removing them.

Any pointers??????

[mcplslg123]

TPS51123 readings are now correct. Do you get light at dc jack now? Have you flashed the main+EC bios?
What is the exact resistance to GND on L6100/6150?